One-way clutches rely on the relative rotation between inner and outer races to switch between a locked mode and a free-wheel mode for the clutch. One-way wedge clutches typically include inner and outer races and a single wedge plate or two wedge plates radially disposed there between. In free-wheel mode, the inner and outer races are rotatable with respect to each other and the at least one wedge plate is rotatable as well. In other words, in free-wheel mode, the extent of the frictional engagement between the at least one wedge plate and the outer race is insufficient to initiate a locked mode. Typically, to initiate a locked mode, in which the inner and outer races and wedge plate are non-rotatably connected, the inner race displaces the wedge plate radially with respect to the outer race. The at least one wedge plate typically includes ramps on the inner diameter; the ramps are operatively arranged to engage correspondingly-shaped ramps on the inner race. Such wedge plates are typically arranged to frictionally engage the outer race via an interference fit. However, wedge clutches of this sort present premature lock-up problems when the inner race rotates with respect to a stationary outer race.
The engagement sequence of a wedge plate typically starts at one circumferential end and wraps around in a circumferential direction as loading takes place. This sequence causes concentrated loading of the outer and inner races at the point of initiation. Thus, typical one-way wedge clutches exhibit non-uniform loading of the wedge clutch components.
Moreover, as the diameter of a one-way wedge clutch increases, the ability to use the wedge plate as a spring to provide a preload force for its engagement decreases. A problem exists surrounding making the wedge plate the appropriate size to provide the appropriate amount of preload required. Additionally, large hysteresis can result from providing a spring that is strong enough to provide the appropriate preload force and resist centrifugal forces.